This application claims the priority of German Application No. 199 60 180.1 filed Dec. 14, 1999, which is incorporated herein by reference.
This invention relates to a method of making a high-explosive projectile having a projectile body which, by means of a thermal post-treatment, is provided with desired fragmentation areas in a portion of its outer surface.
High-explosive projectiles of the above-outlined type are described, for example, in German Patent No. 21 26 351 to which corresponds British Patent No. 1,503,143 and German Offenlegungsschrift (application published without examination) No. 28 37 638, to which corresponds British Patent No. 2,013,842. For improving the fragmentation effect in these known high-explosive projectiles, the desired fragmentation areas are provided directly on the projectile body which, as a rule, is a one-part component. For this purpose, for example, small regions of the projectile body are melted by laser or electron beams and are subsequently cooled in such a manner that metallurgical structural changes (generally narrow martensite zones) are formed, along which the projectile subsequently breaks apart. The above-outlined conventional method is disadvantageous, because by virtue of the substantial heating and cooling of outer surface regions of the projectile body, underlying deeper regions of the projectile body may also be thermally affected, as a result of which a sufficient firing stability of the projectile body and thus the entire high-explosive projectile is frequently not ensured.
It is an object of the invention to provide an improved, simple method of providing a projectile body with desired fragmentation areas by heat treatment without adversely affecting the firing stability of the projectile.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of providing a high-explosive projectile with desired areas of fragmentation includes the following steps: securing a steel plate component in a circumferentially extending recess on the outer surface of a projectile body; directing an energy beam to outer surface portions of the steel plate component; heating, by the energy beam, narrow zones to a temperature above the melting temperature of the steel plate component to a predetermined depth thereof; and cooling the heated zones for effecting structural metallurgical changes in the steel plate component for obtaining the desired areas of fragmentation.
The invention is based essentially on the principle to provide the desired fragmentation areas not directly on the projectile body as it has been done conventionally, but on a separate, shell-like steel plate component located in a suitable recess of the projectile body.
The invention ensures that in addition to securely avoiding a thermal effect on the projectile body, the region of the high-explosive projectile provided with desired fragmentation areas is, upon acceleration of the projectile in the weapon barrel, exposed to significantly lesser stress than the projectile body. This is so because the radial force introduction upon passage of the projectile through the weapon barrel occurs through the ductile projectile body and not through the brittle fragmentation plate or plates. The inner pressure generated by the acceleration of the explosive too, exerts its force solely to the ductile projectile body rather than to the fragmentation shell. The fragmentation plate therefore essentially needs only to support itself.
According to a preferred embodiment of the invention, two curved steel plate portions are inserted in a circumferential recess of the projectile body in such a manner that the steel plate portions circumferentially adjoin one another. Then the steel plate portions are first temporarily secured to the projectile body. The permanent securement of the two steel plate portions is thereafter effected by welding the steel plate portions together as areas of the latter are melted to render those areas brittle. In case the steel plate component is a one-piece tube rather than a longitudinally multi-part member, it has to be connected to the projectile body by suitable securing and/or supporting elements.
It has been found to be advantageous to guide the laser or electron beams required for the local melting of the steel plate component in such a manner that the structural changes extend helically or have a helical crisscross pattern. The generation of helically extending spiral structural changes performed on a projectile body is described, for example, in U.S. Pat. No. 3,783,790.